From clish run "show interface INTERFACE" or from expert mode you can issue the command "ifconfig INTERFACE" and look at the "carrier" counter. This starts at zero when the system boots and increments every time link integrity on that interface is lost. So unplugging the cable, attached switch gets rebooted, etc. Interface state transitions are also logged by syslog in /var/log/messages.
If link integrity is maintained but the next routing hop goes down (so the upstream switch providing link integrity is OK but the upstream router dies or otherwise becomes unavailable) you do have the option to set the "ping" option for the route, and the route will be removed from the table if the next hop does not respond. Generally though this ping option for static routes should only be used if you have more than one route to the same destination, such as a dual default gateway.
The ISP Redundancy feature has ping monitoring as well along with many different real-time notification options for ISP failure.
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